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Underwater Sounds Recorded in Glacier Bay
Background on Acoustic Monitoring
Notes on Sound Samples Recorded in Glacier Bay National Park,
Alaska: Humpback Whales, Killer Whales, Vessels and Ambient Noise
The recordings available here were made by the National Park Service,
using a hydrophone that is anchored near the mouth of Glacier Bay,
Alaska for the purpose of monitoring ambient noise. The recordings
are intended to provide examples of the types of natural and manmade
sounds that occur in Glacier Bay National Park. Most of the samples
are 30 seconds long, but some are longer or shorter. Recordings
are available as files, of various sizes ranging from 94 to
650 KB.
To listen to these sounds you must have an MP3
reader, some of which are available for free on the web.
Important Note on Apparent Loudness of Samples:
Listeners should not conclude that the sound source in one sample
was truly louder than another just because one recording sounds
louder. These samples were taken with the recording equipment set
at various ‘gain’levels, and the subjects were at various
distances from the hydrophone; therefore, the loudnesses of samples
are not comparable.
Click on the headings below to see a list of sound clips. See below
for important notes on various types of recordings.
Whale Sounds
Humpback Whale (Megaptera novaeangliae)
Humpback whale song is thought to be a male breeding display that
is prominent in their wintering grounds, and previously thought
to be quite rare in the feeding areas. It is called a song because
it is a long, complex vocalization that repeats in a predictable
pattern. Whale song recordings from Glacier Bay have been made only
in the fall, when perhaps the hormonal changes that spur whales
to migrate are beginning to occur.
Feeding call is a sterotyped vocalization typically used during
humpback whale coordinated group feeding. In the Glacier Bay area,
it typically occurs 15-20 seconds before a group of whales all surface
together after a foraging dive. This specialized call is common
in some localities but rare in others. It may be used for group
coordination, (ready, set, go!) or to scare/concentrate the schooling
fish that are their prey.
Unstructured sounds. The most common humpback whale vocalization
in Bartlett Cove was the simple “whup”, made with no
discernable pattern. The track entitled “moo etc”is
a sample of common humpback whale vocalizations on a somewhat windy
day. Whales can also make non-vocal sounds by slapping their tail,
flippers or other body parts on the water (for example during a
breach). These sounds can carry for hundreds of meters and seem
to provide another way for whales to communicate with one another
over distance. As you will hear twice near the end of the cut titled
“wheezeblow etc”, even the whale’s breathing can
be audible at some distance, especially wheeze blows. In one of
the recordings, the sound of repeated tail slaps overlaps with the
loud, high-pitched whining of a propeller in bad repair, perhaps
indicating that the sound disturbed the whale.
Killer Whale (Orcinus orca)
Vocalizations of the two most commonly encountered killer whale
forms, the fish-eating (resident) killer whale, and the mammal-eating
(transient) killer whale, are difficult to distinguish by the untrained
ear. However, for the researcher studying killer whale vocalizations
they are almost as distinct as photographic images of the whales.
The vocalizations not only tell the researcher whether the calling
killer whale is a resident or a transient, but also reveal to which
resident or transient population or sub-population the caller belongs.
If the caller is a resident, it furthermore shows who his closest
relatives are. Both residents and transients use discrete calls,
whistles, and clicks. Calls and whistles are used only in social
communication, while clicks are predominantly used in echolocation.
A clicking killer whale produces high frequency sounds and uses
the echoes of those sounds to form images of the areas around him
or her. In much the same way that humans use sonar to investigate
the seafloor, the ultra structure of certain materials, or medical
views of the inside of our bodies, whales use echolocation to orient
and find food in an environment where lighting conditions are poor.
Based on differences in usage of calls, whistles, and clicks, researchers
can tell whether the whales are foraging, resting, or socializing.
For more details on killer whale vocalizations and other features
of their biology, please visit the following sites:
 http://www.killerwhale.org/index2.html
http://www.wildwhales.org
http://www.alaskakillerwhales.org
http://www.whalesalaska.org/
Ambient Noise
Wind and rain are the dominant sources of inanimate natural underwater
sound. As you will know after you’ve heard these cuts, you
can easily tell quite a bit about the weather just by listening.
Whales and other creatures that depend on underwater sound often
have to compensate for background noise from wind, rain, earthquakes,
glaciers and vessels when they communicate with one another.
Vessel Sounds
The recordings of vessels were made at various distances from
the hydrophone, and under a variety of sea conditions, but demonstrate
that different types of vessels can be distinguished from one another.
The humpback whale song recorded with the boat in the foreground
illustrates that whale sounds and manmade sounds co-exist in the
marine environment, with unknown effects on whales and other marine
life.
Other
Animal Sounds
Sometimes we hear sounds on the hydrophone that we can not readily
identify. This record probably contains the sounds of birds swimming
or landing on or near the surface of the water, and remind us that
some sounds are not made intentionally. One of our sound samples
contains bird calls made at the surface that were audible on the
hydrophone.
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